This research concerns itself with the mycotoxins produced by various species of Fusarium in nature, characterization, biosynthesis and action of these toxins; formation of a mycotoxin reference center. The proximate objectives concern zearalenone, an estrogenic substance produced by Fusarium roseum. We have characterized 6 naturally occurring derivatives of the parent compound in an effort to discover more active derivatives. To this end, we have found the cis isomer of zearalenone is 5 times more active than the trans isomer. Zearalenone affects swine in nature more often than other animals and causes infertility. Our experiments show that at 100 ppm of zearalenone in the diet, sows show false pregnancy and at parturition, there are no offspring. At 25 and 50 ppm, the number of piglets are reduced as well as their weight. We are studying the metabolism of zearalenone in swine and rats and to this end have labeled the molecule with tritium and 14C. Studies of metabolites are aided by a maintenance of reference standards in our Mycotoxin Reference Library.